Some of my students find this song a memorable tool to work out which case to use for common prepositions in German:

(to the tune of "She'll be coming round the mountain")

Dative Preps are: aus, bei, mit, nach, seit, von, zu.
Accusative Preps are: durch, für, gegen, ohne, um.
An, auf, hinter, neben, in,
über, unter, vor und zwischen
take the dative when they say where something is
and the accusative when they say where something goes.

It's not my original idea. I'm sure I got it from one of the many wonderful people on the AATG list. I thought I'd share it though because I introduced it to yet another class recently. Even students reluctant to sing still find it useful.